[Xen-devel] Re: POC: ncurses in stubdom

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

Ferenc Wagner, le Tue 28 Apr 2009 22:46:19 +0200, a écrit :
> Samuel Thibault <samuel.thibault@xxxxxxxxxxxx> writes:
> > Ferenc Wagner, le Tue 28 Apr 2009 21:56:07 +0200, a écrit :
> >
> >> But then trying the operation itself provides the exact same
> >> diagnostics.  This is what I mean by "pointless".
> >
> > Ok, but applications could still be upset to see access() work and not
> > open(), or vice-versa.
> 
> Sure, but then they are buggy.

So be they.  We unfortunately can't change all of them just by will.

> >> #if defined(HAVE_POSIX_MEMALIGN)
> >>   if (posix_memalign (&p, align, size) != 0)
> >>     p = 0;
> >> #elif defined(HAVE_MEMALIGN)
> >>   p = memalign (align, size);
> >
> > Errr, so grub2 doesn't unconditionally use posix_memalign.  How did
> > grub2 detect HAVE_POSIX_MEMALIGN?
> 
> By autoconf:
> AC_CHECK_FUNCS(posix_memalign memalign asprintf)

Mmmmm, and I guess it's linking against the host OS, not the stubdom OS,
grmbl.

> > Oh right, sorry.  The final link is not done there but by the minios
> > paragraph of stubdom/Makefile.  You can either set APP_LDLIBS to
> > -lncurses there, to override the empty default of mini-os/Makefile, or
> > add -lncurses to APP_LDLIBS in the ifeq($libc),y) section along others.
> 
> This is what I did in the POC.

Err, in your patch it wasn't in the ifeq section but the empty
declaration.

> > Ferenc Wagner, le Tue 28 Apr 2009 22:02:03 +0200, a écrit :
> >
> >> Eventually it could as well read the terminfo database from the host.
> >> Btw. it tries to do so by invoking a stat() call, and then segfaults
> >> the stubdom.  So there's some problem left here, more serious than
> >> access().
> >
> > Right, I'm not sure we really want to have a stubdom do this.
> 
> Do you mean accessing the host filesystem?  I agree that shouldn't be
> made necessary, as stubdoms are a security measure in part.

Yes.

Samuel

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